Yeah, with a .6 OD, a 3.07-8 would be to high on the highway, 3.5 is a better call. Cam profile, flywheel weight, torque, driver habits, cruise rpm at a reasonable mph (70 is reasonable), trans OD ratio, all these things come into play.
I don't drag much, maybe a couple of times a year is all, so I'm primarily concerned with driving around town wheel spin, which is to much for my taste. That is tempting to consider a swap to a higher rear gear ratio. My main problem there is I don't want to do all the work! OK, I'll buy it for a good price, now, who's coming over to put it in? Pizza is on me...
I had mine out as well, ran a few errands, about 50 degrees here, not to bad. That new heater works well!